1. Field of the Invention
The present invention relates to a broadband wireless communication system. More particularly, the present invention relates to an apparatus and method for performing capability negotiation for a Hybrid Automatic Repeat reQuest (HARQ) parameter in the broadband wireless communication system.
2. Description of the Related Art
A Hybrid Automatic Repeat reQuest (HARQ) scheme is employed to increase data transmission efficiency in a wireless communication system of the related art and a next generation wireless communication system such as 3rd Generation Partnership Project Long Term Evolution (3GPP LTE), Worldwide Interoperability for Microwave Access (WiMAX), etc. The HARQ scheme is proposed to correct a data error in a more rapid manner.
While the Automatic Repeat reQuest (ARQ) scheme of the related art determines whether to retransmit reception data by determining an error of data received in a software manner, the HARQ scheme determines whether to perform retransmission by determining the error of the reception data in a hardware manner. Therefore, a system employing the HARQ scheme can rapidly detect an error of received data. In addition, higher reception performance can be obtained by combining Log Likelihood Ratio (LLR) values of retransmission data and initially transmitted data.
In order to apply the HARQ scheme, the HARQ-related configuration parameters have to be pre-determined between a transmitter and a receiver. For example, the configuration parameters may include an uplink/downlink HARQ channel location, a signal binding scheme, a maximum number of retransmissions, etc. When each of the parameters is directly negotiated, a signaling overhead is increased according to the number of parameters. Accordingly, in order to decrease the signaling overhead, the transmitter and the receiver can define a specific number of parameter combinations, and can perform negotiation by using an index allocated to each combination. For example, an Institute of Electrical and Electronics Engineers (IEEE) 802.16e standard defines 5 parameter combinations in the name of an HARQ set.
The number of required HARQ sets may be increased as a system is enhanced. However, since the system is optimized for the support of the HARQ sets defined according to the related art, a newly added HARQ set cannot be indicated. If there is a value not used in a field for indicating the HARQ set and if a new HARQ set is indicated by using the unused value, then a transmitter and a receiver which recognize the new HARQ set can interpret the HARQ set without an error whereas such an error-free interpretation may not be possible when using the legacy transmitter and receiver. Therefore, the legacy transmitter and receiver may apply an incorrect HARQ parameter, or may face a situation where an access is denied.
Accordingly, there is a need for a method for indicating a newly defined HARQ set without an occurrence of an interpretation error when using the legacy transmitter and receiver.